Nonaqueous electrolyte secondary batteries typified by lithium-ion secondary batteries each have a high energy density. Thus, such nonaqueous electrolyte secondary batteries are currently in wide use as batteries for devices such as a personal computer, a mobile phone, and a portable information terminal. Such nonaqueous electrolyte secondary batteries have recently been developed as on-vehicle batteries as well.
In a nonaqueous electrolyte secondary battery, the electrodes expand and contract repeatedly as the nonaqueous electrolyte secondary battery is charged and discharged. The electrodes and the separator thus cause stress on each other. This, for example, causes the electrode active materials to fall off and consequently increases the internal resistance, unfortunately resulting in a degraded cycle characteristic. In view of that, there has been proposed a technique of coating the surface of a separator with an adhesive material such as polyvinylidene fluoride for increased adhesiveness between the separator and electrodes (see Patent Literatures 1 and 2). Coating a separator with an adhesive material, however, has been causing the separator to curl visibly. A curled separator cannot be handled easily during production, which may unfortunately lead to problems during battery preparation such as defective rolling and defective assembly.